The present invention relates to a method of preparing a partial one-shot electron beam exposure mask, and a method of direct-writing patterns by use of a partial one-shot electron beam exposure.
In recent years, a design rule requires a scaling down or downsizing of mask patterns to be used for a lithography. The lithography is classified into a photo-lithography, an X-ray lithography and an electron beam lithography. The X-ray lithography and the electron beam lithography are more attractive as the next generation lithography as being responsible for the scaling down or the downsizing in accordance with the requirement of the design rule. Further, a high throughput is required for manufacturing semiconductor devices. The high throughput is also required for the lithography for writing fine patterns on a resist over a wafer. A projection mode electron beam exposure has been proposed which uses an electron beam mask with fine patterns which are to be projected onto the resist over the wafer. This electron beam mask with some predetermined fine patterns is used for a partial one-shot of the electron beam. The partial one-shot electron beam mask has an aperture for a variable shaped electron beam exposure and some predetermined aperture patterns which, for example, correspond to contact hole patterns and line&space patterns. Such predetermined aperture patterns are extracted from device design data or computer aided design data. The predetermined aperture patterns of the mask constitute unit cells or structures which repeat a large number of times. This is disclosed in, for example, the Japanese laid-open patent publication No. 5-13313.
The mask for the partial one-shot direct-writing is prepared by use of CAD-data which have been prepared in a conventional method of preparation of the partial one-shot direct-writing mask data. The fine patterns are written by use of the mask prepared. If, however, the fine patterns are divided on the CAD-data, then the repeating unit cell or structure including the divided patterns is extracted for couductios a partial one-shot. This may cause a displacement between the partial one-shots or a deformation such as disconnection of the pattern. For example, as illustrated in FIG. 1, contact hole patterns are divided into repeating unit cells 1, each of which has a plurality of rectangles half-divided from the square-shaped control hole pattern for preparation of CAD-data 3. The repeating unit cell 1 is extracted from the CAD-data for forming an aperture pattern on a partial one-shot mask 2. For this reason, as illustrated in FIG. 2, there might be caused a disconnection "C" of the contact hole pattern or a displacement "D" between divided rectangular-shaped parts of the contact hole patter.
In the above circumstances, it had been required for conducting the electron beam partial one-shot direct-writing to optimize an extraction of partial one-shot mask data independently from the repeating unit cells on the CAD-data for preparing a mask in accordance with the extracted partial one-shot mask data so as to improve an accuracy of writing the pattern on the resist.